Factors promoting colonization by legionellae in residential water distribution systems: an environmental case-control survey

As part of a case-control study of community-acquired Legionnaires' disease, several factors related to residential water distribution systems and public drinking water systems were studied in the homes of 124 patients with community-acquired Legionnaire's disease and in the homes of 354 controls. The presence of water reservoirs and hot water tanks was studied in residential systems. Factors such as deficient chlorine levels, pipe repairs and other work, water flow interruptions, the use of alternative water sources, inadequate cleaning operations in public water reservoirs, and the position of the home within the public network (and whether this location constituted an endpoint) were studied in public water supply systems. Levels of legionellae in domestic water samples were also measured. Although the use of water reservoirs and hot water tanks promotes colonization by legionellae in residential systems, none of the variables studied seems to increase the incidence of community-acquired Legionnaires' disease.

Influence of lipopolysaccharide chemotype on the interaction between Klebsiella pneumoniae and human polymorphonuclear leucocytes

A series of isogenic mutants lacking either the O1 (O-:K66) or K66 (O1:K-) antigens or both (O-:K-), some of which had additional defects in their LPS core polysaccharide was used to examine the interaction between polymorphonuclear leucocytes (PMNLs) and K. pneumoniae serotype O1:K66. In the absence of serum complement, only a O-:K- strain with a deep rough LPS chemotype elicited a PMNL-dependent chemiluminescent (CL) response. However, following opsonization of the non-capsulated strains by complement, the largest CL response was to the O1:K- mutant. This mutant also activated and bound more complement C3 than any of the other encapsulated or non-capsulated strains examined. Despite the surface exposure of smooth and rough LPS in the encapsulated parent and mutant strains, the K66 antigen reduced the binding of C3 and prevented PMNL activation. Both anti-LPS and anti-K66 antibodies, however, stimulated a PMNL-dependent CL response to the K66 bearing strains.

Isolation and characterization of Klebsiella pneumoniae unencapsulated mutants

Klebsiella pneumoniae mutants were obtained after UV irradiation and negative selection with anticapsular serum. Unencapsulation, rather than expression of a structurally altered capsule, was found in the mutants. The mutant strains showed no alterations in their outer membrane proteins and lipopolysaccharide, and a great similarity with the wild type in the properties tested (serum resistance, antimicrobial sensitivity, and lipopolysaccharide-specific bacteriophage sensitivity), with the exception of a higher cell surface hydrophobicity and resistance to bacteriophage FC3-9.

A high molecular weight lipopolysaccharide specific bacteriophage for Klebsiella pneumoniae

High-molecular weight lipopolysaccharide (O antigen enriched fraction) from Klebsiella pneumoniae was determined to be the receptor for bacteriophage FC3-1. A methodology for the identification of the lipopolysaccharide component involved in FC3-1 bacteriophage reception was used that is suitable for other phages and host bacteria.

Role of lipopolysaccharide and complement in susceptibility of Escherichia coli and Salmonella typhimurium to non-immune serum

The role of lipopolysaccharide (LPS) in the susceptibility of Escherichia coli and Salmonella typhimurium to non-immune human serum was investigated using serum-sensitive strains of both enterobacteria. LPS from serum-resistant strains of E. coli and S. typhimurium could activate and completely remove the serum bactericidal activity, and also showed dose-dependent anti-complement activity. These properties were mainly due to the high-molecular-mass LPS: the low-molecular-mass LPS from serum-resistant strains of E. coli and S. typhimurium had only a slight effect on the serum bactericidal activity, and showed only low anti-complement activity, even at high concentration. The results suggest that LPS composition, especially the O-antigen polysaccharide chains, contributes to the susceptibility of E. coli and S. typhimurium strains to complement-mediated serum bactericidal activity.

Role of lipopolysaccharide and complement in susceptibility of Klebsiella pneumoniae to nonimmune serum

The role of lipopolysaccharide (LPS) in the susceptibility of Klebsiella pneumoniae to serum and the mechanism of complement activation by serum-susceptible (SerS) strains were investigated. The classical and alternative complement pathways are involved in serum killing of susceptible K. pneumoniae strains. The LPS composition seems to play a very important role in the serum bactericidal reaction, while capsular polysaccharide from this bacterium does not play any role. High-molecular-weight LPS from serum-resistant (Serr) K. pneumoniae strains was able to inhibit completely the serum bactericidal activity. LPS from SerS K. pneumoniae strains was not able to inhibit completely the serum bactericidal activity; low-molecular-weight LPS from Serr K. pneumoniae strains could not either. All these findings suggested that LPS composition, especially the O-antigen polysaccharide chains, contributes to the susceptibility of K. pneumoniae strains to complement-mediated serum bactericidal activity.

Role of capsule and O antigen in resistance of Klebsiella pneumoniae to serum bactericidal activity

The ability of Klebsiella pneumoniae strains to resist the bactericidal activity of serum was quantitated. The K. pneumoniae strains tested included mutants lacking the capsular polysaccharide and mutants having a modified lipopolysaccharide structure. The last mutants were obtained as phage-resistant mutants, and their lipopolysaccharide was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and chemical analysis. Serum-resistant mutants derived from phage-resistant mutants (lipopolysaccharide mutants) were also characterized. Resistance to the bactericidal activity of complement was mediated by the lipopolysaccharide, especially by the O-antigen polysaccharide chains. The capsular polysaccharide seemed not to play any important role in resistance to serum bactericidal activity in this bacterium.

New, simple medium for selective, differential recovery of Klebsiella spp

A highly selective, differential medium for the enumeration and isolation of Klebsiella spp. was developed. With pure cultures, 100% recovery of Klebsiella spp. was observed. Recovery of Klebsiella spp. on MacConkey-inositol-potassium tellurite (MCIK) agar was as good as or better than on MacConkey-inositol-carbenicillin agar either with pure cultures or environmental samples. Recovery and percent colony confirmation with MCIK agar were greater and easier to obtain than for other proposed Klebsiella selective media.